The present invention relates to the field of intravenous supply alarm systems.
Intravenous supply systems are widely used in medical treatments to supply nutrients, drugs, blood or blood products, etc. to patients. While intravenous (IV) supply systems have been used for many years, several improvements have been made to increase the safety and utility of the systems. The most notable improvement has been the disposable IV supply system.
Disposable IV systems are commonly fabricated from a clear thermoplastic material which is formed into a bladder or bag. The appropriate tubing and needle are integrally attached and the bladder is pre-filled with sterile intravenous fluids and is thus self-contained, requiring no extra equipment when used.
The plastic material and construction techniques employed allow the disposable IV supply systems to be fabricated at a minimal cost. They are thus immediately ready to use, when needed and may be conveniently discarded after use, removing any possibility of contamination of the supply or infection of a patient through reuse.
However, a problem exists with IV supply systems in general in that when the IV supply is exhausted, there is a possibility that an air bubble may be allowed to enter the patient's vein through the feed tubing. This air bubble may lead to the formation of an air embolism with serious consequences to the patient.
Thus, it is necessary for medical personnel, or the patient, to closely monitor the level of fluid in the supply at all times. Placing this responsibility on the patient leads to increased anxiety and general discontent with the use of the IV supply systems. There have been several prior attempts to overcome the problem of monitoring the supply level in IV systems.
U.S. Pat. No. 2,706,755 to Krasno shows an alarm device from which an intravenous supply bottle is hung. The device has a moveable plate which is biased by a spring against two electrical contacts to complete an electric alarm circuit. The supply bottle is suspended from a hook attached to the plate and the weight o the bottle and its contents act against the spring to move the plate away from the electrical contacts, opening the circuit. As the contents of the supply bottle are fed into the patient, the weight acting against the spring is reduced and the plate moves towards the electrical contacts. When the supply is almost fully displaced from the bottle, the weight is reduced to the point that the plate completes the circuit and activates the alarm.
U.S. Pat. No. 3,389,387 to Hulse et al. shows a similar alarm device which monitors changes in the weight of the supply container due to changes in the amount of supply fluid. As the container empties, a spring biased member is moved from a position in contact with a circuit-opening switch to a position out of contact with this switch thus closing the circuit and signalling a medical attendant.
U.S Pat. No. 3,390,238 to O'Neill shows a fairly complex alarm device which is adjustable to accommodate supply assemblies of different weights, due to differing amounts of supply fluid and/or different densities of various supply fluids.
These prior alarm devices all suffer from numerous disadvantages in practise. Firstly, they are bulky units, separate from the IV containers, which must be set up in association with the IV containers prior to use. In current medical practice, however, it is desirable that all treatments and apparatus be self-contained whenever possible. Secondly, they must be re-used and transferred from one IV container to the next thus increasing the likelihood of breakage. Thirdly, repeated use of these units necessitates repairs and performance monitoring. Fourthly, these units are expensive to manufacture with numerous and detailed component parts. Due to the aforementioned problems, these devices have not attracted significant commercial interest.